This article explains how to fix the 'No Accessible Software Data' error on the 3DS. Instructions apply to all models of Nintendo 3DS.
How to Fix Micro SD Management 3ds (Cannot Access // Error)
To fix this error, copy your game and save data to the hard drive to keep it intact while removing the memory card from the 3DS to clear the corruption. Follow these steps to repair the card without losing your progress, photos, or profile.
Power off the hardware and disconnect the power adapter, if connected.
Flip the 3DS over and use a small Phillips screwdriver to unscrew the two screws at the top of the back panel.
